Through the endoscope, balloon dilation of tight esophageal strictures is frequently carried out with fluoroscopic monitoring. A stricture is considered to be “tight” if an endoscope cannot be passed through it. Fluoroscopic monitoring of tight stricture dilation is believed to help prevent sudden fracture or splitting of the stricture and thus reduce the risk of esophageal perforation during the dilation procedure. Currently available dilation balloons are made of transparent material. However, the tapered or domed butt design of the proximal end of currently available dilation balloons severely limits stricture wall visualization when the face of the endoscope is approximated to the butt of the balloon. Also, the misalignment produced by current dilation balloon design between the dilation balloon and endoscope insertion shaft as described below further limits stricture wall visualization. Therefore, fluoroscopic monitoring must be relied upon for monitoring purposes.
Examination and accurate measurement of an esophageal stricture can only be accomplished visually or endosonographically if the endoscope can be passed completely through the stricture. Two techniques exist for accomplishing complete stricture passage with balloon dilation. The traditional method is to pass and inflate successively larger balloons across the stricture until a diameter of 15 to 16 mm is achieved. The last dilation balloon is then removed and the instrument is maneuvered through the stricture under direct unguided operator control. The post-dilation 15 or 16 mm diameter stricture lumen is 5 or 6 mm larger than the diameter of a standard video endoscope and 2 to 3 mm larger than the diameter of an echoendoscope. However, stricture elasticity, luminal tortuosity, and frequent shelving (stepped areas along the stricture) can prevent passage of the instrument, despite an apparently adequate dilation.
An alternative method for accomplishing complete stricture passage with balloon dilation is the “balloon-scope train method”. The stricture is dilated to a diameter 1 or 2 mm larger than the diameter of the endoscope. The endoscope is then pushed up against the proximal end of the inflated dilation balloon to form a balloon-scope “train”. The combination of balloon and endoscope is then advanced through the stricture. Although currently available dilation balloons are made of transparent material, their design permits only limited monitoring and inspection of the stricture wall as the maneuver is carried out.
Unfortunately, current dilation balloon design hinders not only visualization of the stricture wall during dilation and subsequent instrument passage, but also actively impedes the passage of the “balloon-scope train”. FIG. 1 depicts a currently available esophageal dilation balloon (for example, the QUANTUM TTC® Balloon Dilator, which is the subject of U.S. Pat. No. 5,681,344 to Kelly) and endoscope in a “balloon-scope train” configuration. Because the instrument accessory channel outlet on the endoscope face is off-center with respect to the endoscope insertion shaft and the balloon support wire is centered with respect to the balloon, the flat face of the endoscope protrudes over one side of the balloon. The protruding endoscope face tends to catch tumor shelves and resist passage through tortuous areas resulting in difficult passage and on occasion failure of passage. Also, because the current tapered or domed butt balloon designs prevent the endoscope from being cinched up tight against the rear of the balloon, a significant gap is created, which exacerbates the tendency of the endoscope face to catch on tumor shelves and in tortuous areas of a stricture.
What is needed is a dilation balloon that will permit direct visualization of the stricture wall through the transparent material of the balloon for purposes of stricture wall monitoring during dilation and that will align properly with the insertion shaft of the endoscope to facilitate passage of the endoscope through the stricture using the balloon-scope train method.